1. Technical Field
The invention relates to the field of rotary joints for the transmission of a signal, and more particularly, or conducting an optical signal between two points.
2. Background Art
The fiber optic rotary flex is a limited rotation device that will allow for the inclusion of single-mode and multi-mode fiber optic channels in standard polytwists. Optical fibers pass through the shaft protected by a small diameter rigid tube. The tube not only protects the fiber from accidental breakage, it controls the bend radius, thus limiting power loss. As the tube exits into the flange, the fiber passes from the rigid tubing into flexible tubing. The fiber is then wound around the rotating axis, in a perpendicular plane to that axis, with enough wraps to provide the necessary amount of travel. As the industry begins to rely more and more on high speed data links, the use of optical fiber in a rotary component system should increase.
It is believed that the present invention offers many advantages to known limited rotation products (polytwists):
The present device is very small and can easily be retrofitted into current designs. This allows the advantage of high speed data transmission while maintaining currently designed and qualified parts.
When bend radii are properly formed, losses are very low; less than 1 dB.
Manufacturing costs are extremely low. When used as a retrofit in a current design, tooling should be unaffected.
The present invention can be used with single mode or multi mode fiber.
The optical cable is subject to a low torque.
The known solution to transmitting optical signals across a rotating interface involves either a fiber optic rotary joint or a cable wrap. U.S. Pat. No. 4,710,131, issued Dec. 1, 1987, is an example of such known fiber optic rotary joint. The known rotary joint will allow unlimited rotation in either direction; however, it is much more costly and much larger in size. It is also very difficult to incorporate into existing designs. The cable wrap is a generally unreliable answer to rotary component needs. They are bulky, hard to install, and torque response uniformity is hard to maintain from part to part.
While the above cited references introduce and disclose a number of noteworthy advances and technological improvements within the art, none completely fulfills the specific objectives achieved by this invention.
In accordance with the present invention, a rotary hub unit for a transmission cable includes a stationary hub having a longitudinal axis therethrough. An angular transition portion of a desired transmission cable transmits a signal between a first junction end mounted with the stationary hub to a second end junction mounted with the stationary junction hub. The first junction end of the angular transition portion should be essentially perpendicular to the second junction end.
A housing unit is rotatably mounted about the longitudinal axis of the stationary hub, and has an interior that is adapted to receive a portion of transmission cable. A coiled portion of transmission cable is formed about the longitudinal axis of the stationary hub in the housing interior. The coiled portion of the transmission cable has a first end that is mated with the second junction end of the angular transition portion, and also an outer end for transmitting the signal out of the housing.
The rotary hub unit permits limited movement of the outer end of the transmission cable coil relative to the longitudinal axis of the stationary hub.
These and other objects, advantages and features of this invention will be apparent from the following description taken with reference to the accompanying drawings, wherein is shown the preferred embodiments of the invention